1. Field of the Invention
The present invention relates to a sensor for capacitive detection of a mechanical deflection, and a method for capacitive detection of a mechanical deflection.
2. Description of Related Art
Micromechanical sensors such as acceleration sensors, yaw rate sensors, or pressure sensors are frequently used. A conventional form of evaluation of such sensors is the capacitive evaluation in which a deflection induced by the variable to be measured is converted to a change in capacitance, which is then evaluated electrically. In the case of inertial sensors, this is usually accomplished via a differential capacitor which includes two stationary electrodes and a movable electrode situated therebetween. In the case of movement of the movable electrode, capacitances C1 and C2 change in opposite directions between the movable electrode and the two stationary electrodes. This change is usually evaluated as a so-called ΔC/C evaluation, the following equation applying for the output signal:
      U    out    =                              C          1                -                  C          2                                      C          1                +                  C          2                +                  2          ⁢                      C            p                                ⁢          U      ref      
So-called parasitic capacitances Cp may include various contributions, depending on the partitioning concept and the type of sensor. Stray fields on the sensor structure, on the solder points (pads), and on the wires (bond wires) may contribute to parasitic capacitances Cp. Since capacitances C1 and C2 contain information about the measuring signal, parasitic capacitances Cp may influence the sensitivity of traditional sensors. In particular, process-induced fluctuations in parasitic capacitances Cp due to bond wire drift, for example, may result in variations in sensitivity, which may subsequently necessitate a separate sensitivity adjustment of the sensor.